X-ray sensitive film has been used in X-ray imaging conventionally employed for medical and industrial purposes, but radiation imaging systems that use a radiation detecting element have become increasingly popular from the standpoint of convenience and durability of the imaging result. In this type of radiation imaging system, two-dimensional image data derived from radiation is obtained as electrical signals using a radiation detecting element having a plurality of pixels, these signals are processed by a processing apparatus and displayed on a monitor. A representative radiation detecting element has a construction in which scintillator is incorporated in light detectors arranged in a one-dimensional or two-dimensional pattern and incident radiation is converted into light such as visible light by this scintillator and detected.
CsI, which is a typical scintillator material, is a moisture-absorbing material that absorbs atmospheric water vapor (moisture) and dissolves. Because the characteristics of the scintillator, particularly the resolution, deteriorate as a result, the scintillator must have a construction whereby they are protected from atmospheric moisture. As a construction whereby scintillator is protected from atmospheric moisture, the technologies disclosed in JP 05-196742A and in JP 05-242841A, as well as in International Publication Nos. WO-98/36290 and WO-98/36291 are known.